1. Field of the Invention
This invention relates to a velocity-reduced drive system, and more particularly to a small or flat velocity-reduced drive system for operating a small device like a video camera or a combined camera-and-video-tape-recorder unit by reducing the velocity of a motor.
2. Description of the Related Art
It is necessary to reduce the velocity of a motor for a lens driving unit when such unit is operated for focusing or zooming a video camera or a combined camera-and-video-tape-recorder unit (hereinafter called camera-and-VTR unit). One of such velocity-reduced drive systems was proposed in Japanese Patent Laid-Open Publication No. 74342/1989. With the cited system, the velocity of the motor is reduced by a reduction gear train or by combination of the reduction gear train and a pulley-belt unit. A drive shaft of the motor and an output shaft are positioned in the same direction.
Conventionally, the motor and a case for the reduction gear unit are piled with the drive shaft and the output shaft facing in the same direction. Therefore, the drive shaft inevitably becomes longer. The reduction gear train includes a plurality of spur gears, which generate relatively high sounds. Such high sounds are picked up by a microphone of the video camera, being reproduced as noises. Since the direction of the output shaft is limited, the velocity-reduced drive system would have narrower application fields. Further, a number of the spur gears have to be used to obtain large velocity reductions, which means increase of component parts.
When the velocity-reduced drive system is used to operate a cylindrical movable member (e.g. a lens barrel of a combined camera-and-VTR unit), there would be formed an undesired space around the flat surface of the drive system and the cylindrical member.